The two men running for San Diego mayor rarely see eye-to-eye on anything, but Republican City Councilman Carl DeMaio and Democratic Rep. Bob Filner do agree on one thing: If you want to know how they’ll govern as mayor, look at the stance they took earlier this year on the proposed convention center expansion.

DeMaio has adamantly opposed tax increases yet voted in favor of the expansion’s financing plan, which calls for hotel surcharges to cover a bulk of the $520 million cost. He called it a thoughtful and balanced solution to aid the local economy that is largely paid for by hotels. DeMaio accused Filner of using the issue as a political football during a campaign by siding with unions in opposition.

Filner, who supports an expansion, adamantly opposed the plan and called it “the most blatant giveaway” of taxpayer money he’s ever seen. He said a public tax should be put to a public vote and accused city leaders of allowing a small but powerful group — hoteliers — too much say over a major economic engine. Filner accused DeMaio of kowtowing to the special interests that back his campaign by voting for the proposal.

The differing opinions on the project will likely have ramifications beyond the campaign trail. The expansion is anything but certain, as only the financing plan has won approval by the City Council and has yet to be validated in court. In other words, current Mayor Jerry Sanders got the ball rolling, but the next mayor will need to shepherd the project through the California Coastal Commission as labor and environmentalists voice their misgivings.

DeMaio says his opponent’s outspoken opposition to the proposal shows he’s not ready to assume leadership of the nation’s eighth largest city.

“You have one mayoral candidate who is trying to divide and derail an important project for political gain,” he said. “When you have a project like this that could put San Diegans back to work, that will bring millions of dollars in for municipal services, it’s a shame that some folks would seek to divide and derail rather than unite and move our city forward.”

Filner, who last month said he would support the plan as mayor if a court deems it legal, said the City Council approval of the financing plan is exactly why the city needs someone like him as the next mayor.

“They thought nothing of giving one private group … the authority to control all this money,” Filner said. “That’s got to change. That’s what I represent. Who’s going to be looking out for the public in all this? It’s been a small group of people that control these decisions. … I watched this stuff in utter disbelief. Usually they’re more subtle about giving away public money. This was so blatant. That’s going to be the biggest change here when I’m mayor.”

The proposed $520 million expansion calls for about 220,150 square feet of additional exhibit hall space for a combined total of 745,850 square feet, as well as 101,500 more square feet of meeting rooms and 78,470 square feet of ballroom space. The extra space is needed, supporters say, to retain major events such as Comic-Con and compete with other cities for coveted trade shows, all of which boost the local economy.

The bulk of the financing for the expansion will come from a hotel tax already approved by the city’s hotel owners, although the city is awaiting a ruling from a judge validating its legality. Should the room surcharge go into effect, guests at hotels closest to the convention center would have to pay an additional 3 percent on their room bills. Those staying in Mission Valley, Mission Bay and around the airport would pay an extra 2 percent. The rest of the city’s hotels would add a 1 percent increase. Hotel guests currently pay a room tax of 12.5 percent.

What Filner considers the “giveaway” part of the deal is that to get hoteliers to vote in favor of the plan, the San Diego Convention & Visitors Bureau won marketing control over the convention center, including $3.1 million annually in center funds.

Filner said it gives private industry far too much control over a public asset. DeMaio said he’d much rather have the private groups who have skin in the game in charge of marketing than government bureaucrats.

Filner said he’s the only candidate who can make the expansion a reality because his strong relationships with unions and environmentalists over the years mean he’ll be able to get them to drop their objections. He said he’ll do that by making them part of the project, either through jobs or changing the expansion’s aesthetics.

“When you give people a stake in what’s going on, people have a confidence and a more positive attitude,” he said. “If the convention center vote is validated … they have to go to the Coastal Commission. People think labor and environmentalists can block it there. But what if they were part of the action, and I made them part of the action? I think we can get their approval of it. I don’t think Carl can. I think I can get that convention center approved, where he’s going to have major problems.”

DeMaio, who has battled with labor over pension benefits for years, said Filner can’t be trusted on a major civic project like the convention center expansion.

“He changes his views on issues more times than he changes his socks in a week,” DeMaio said. “You need a leader who’s consistent, who’s thoughtful and takes positions based on principle rather than political convenience. What he says today is not reliable, and it creates a chaos. It divides. It creates distrust, and these are not the qualities that we need in the Mayor’s Office at City Hall.”

The comment period for the project’s environmental impact report has ended, setting the stage for certification of the document this year by San Diego port commissioners. The EIR for the project, which must be approved by the Coastal Commission, identifies impacts large and small in a number of areas, from aesthetics and air quality to noise and traffic. In the report, measures are recommended for overcoming those impacts, including rooftop solar panels and low-water plantings in the landscaping.